1. Field of Invention
This invention pertains generally to wrenches and other tools and, more particularly, to apparatus for applying a driving torque to a driven element.
2. Description of Prior Art
It is common practice to use rotatively driven mechanical devices to draw two objects together or to push two objects apart. Common examples of devices for drawing objects together are bolts and nuts, and an example of a device for pushing objects apart is a jack screw. Such devices commonly have some feature that makes it possible to rotate them with a tool. A nut or the head of a bolt, for example, might have a hexagonal shape, a square shape, or another shape suitable for engagement by a wrench, and the head of a bolt or screw may be provided with a slot or other suitable opening for engagement by a screwdriver.
It is frequently desirable to be able to engage these devices with a tool to provide continuous rotation of the device without having to disengage and re-engage the tool for each successive increment of rotation. This continuous turning capability is particularly useful in situations where time is critical or space is limited.
Heretofore, some tools have been provided for continuous mating engagement with bolts, nuts and the like to apply a driving torque to them. Common examples of such tools include socket wrenches with ratcheting handles and certain box wrenches with ratcheting mechanisms. However, the tools heretofore provided of this type have one common drawback that severely limits their use. They require that the end of the nut, bolt or other driven device be unobstructed and accessible because the tool must be placed on or over the end of the device to apply the torquing force.
Many times the ends of the driven devices are covered, obstructed or otherwise not accessible, in which case continuously engaged torquing tools cannot be used, and some other tool such as an open end wrench or a pair of pliers must be employed. These other tools do not allow continuous turning of the driven device, but instead require that the tool be disengaged and re-engaged for successive increments of rotation. The process of repeatedly repositioning the tool and making only a limited degree of rotation with each positioning is inefficient and time consuming. It is especially undesirable and difficult when working in small, confined spaces like those that often occur when performing surgical procedures.
One surgical procedure where space for manipulation of a wrench is limited is back fusion surgery. In back fusion surgery, a spinal bone separating device is often used to separate the spinal bones in preparation for the bone fusion. Such a bone separation device consists of two threaded hooks that engage the bones to be separated. These hooks mount on oppositely threaded sections of a jack screw which is rotated by means of a hex shaped nut affixed to the screw between the oppositely threaded sections. Access to the nut from the ends of the screw is blocked by the hooks so that a continuously engaged torquing tool such as a socket wrench cannot be utilized to turn the screw. An open ended box wrench is the tool which is currently used in this situation. With this tool, the limited space available and the limited visibility in such surgery, the task of separating the bones is extremely difficult and time consuming for doctors to perform.